The system is freely available for any peaceful and noncommercial applications.
For other purposes, write to the author.

Version 1.2 is adapted to changes in SWI Prolog version 7; it is expected also to work
with earlier versions of SWI Prolog.
Version 1.1 differs from 1.0 by fixing a few minor issues.
Version 1.0 is adapted from an earlier version 0.1 from 2002, that
ran under SICStus Prolog 3.
Earlier versions of CHRG are not available.

CHRG stands for "CHR Grammars" and is a logical grammar system
based on
CHR, analogously to the way
Definite Clause Grammars are defined and implemented
on top of Prolog.
CHR is an extension to Prolog originally intended for writing
constraint solvers in a declarative way, but it is also relevant
for language processing as it provides a natural framework for bottom-up
evaluation and easy ways to manipulate different kinds of hypotheses.
-- CHRG provides the grammatical interface to CHR.